The invention relates to bag filter apparatus that is adapted to receive gas carrying a quantity of dust or other particulate matter and permit clean gas to flow therethrough while retaining the particulate matter on the surface of the filter. To remove dust deposits therefrom, a series of laterally aligned nozzles are adapted to exhaust a blast of compressed air into the open end of each filter bag. Such a reverse blast of air causes a momentary reversal of gas flow through each filter bag and flexing of the filter that loosens particulate matter collected on the outer surface thereof so the dust will fall off and each bag may be returned to a clean condition whereby collecting effectiveness may be restored.
A header carrying a series of spaced nozzles is concentrically positioned above the open end of each filter bag in order that compressed air exhausting from a nozzle diverges and closes off the normal flow of carrier gas through each filter bag. If the header should become slightly twisted or distorted whereby the nozzle will exhaust a blast of compressed air obliquely toward the end of the adjacent filter bag, normal fluid flow in the opposite direction will not be stopped, so reverse flexing of the filter bags will not take place, and the cleaning arrangement will not be effective. Thus, the arrangement defined herein will preclude thermal distortion of the header during normal operation. Furthermore, the arrangement defined will permit the bag filter assembly to be quickly and precisely re-assembled after disassembly to maintain a high operating effectiveness.
Prior art cleaning arrangements have variously described nozzles for discharging compressed air into the open ends of aligned porous filter bags, but none is known to precisely locate each nozzle with respect to each bag. U.S. Pat. Nos. 3,733,784 and 4,157,901 simply show a header pipe with nozzles that exhaust compressed air into the open end of a series of adjacent filter bags. Thermal distortion of an unsupported header pipe would direct the cleaning air obliquely away from the open end of an adjacent filter bag so cleaning would be less than optimum.
U.S. Pat. Nos. 3,926,595 and 3,680,285 show header pipes with nozzles that direct a reverse flow of cleaning gas into the open ends of adjacent bag filters. The header pipes are supported at opposite ends by the walls of a housing, but there is no provision for dismantling the header pipes or containing the inevitable thermal distortion that will take place when a temperature change occurs.